Internal pedicle shield

ABSTRACT

A pedicle insulator implant is designed to protect the nerves and surrounding tissue from injury by pedicle screws or other surgical devices and instruments. In its basic structure, the implant has a thicker section and a thinner section, the thicker section providing protection for nerves and other sensitive tissues while the thinner section can be deformable and provides grip. In one variation of the basic structure, the thinner section possess a rough surface when it is desirable in situations to provide further grip of the assembly and prevent rotation during the insertion of, for example, a pedicle screw.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S.Patent Application No. 15,975,308, filed May 9, 2018, now allowed,entitled “INTERNAL PEDICLE INSULATOR”, which is a continuation of U.S.patent application Ser. No. 14/723,620, filed May 28, 2015, now U.S.Pat. No. 9,993,268, entitled “INTERNAL PEDICLE INSULATOR” which claimsthe benefit of and priority to U.S. Provisional Patent Application No.62/003,978, entitled “INTERNAL PEDICLE INSULATOR”, filed May 28, 2014.The application is related to U.S. patent application Ser. No.11/712,257 which is a Continuation in Part of U.S. Pat. No. 7,338,500.The contents of the above referenced applications are incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to surgical instruments and tools. In particular,pedicle insulator assemblies and methods of insertion are described.

BACKGROUND

Spinal fusion typically involves the removal of damaged disc materialbetween two adjacent vertebrae and the subsequent insertion of one ormore interbody devices into the emptied disc space, either using ananterior or a posterior approach. In order to ensure primary stability,the surgeon usually adopts a fixation system that is anchored to thespine by means of orthopedic screws implanted into the pedicles of thevertebrae that are to be fused together. The single screws are connectedtogether by means of rigid or semi-rigid rods, which are convenientlyhoused within a transversal hole provided in the screw head.

Since the FDA approval of pedicle screws, approximately 200,000instrumented fusions occur each year in the US. There is very limitedtolerance between the pedicle screw and the nerve root with theinferomedial wall of the pedicle (approx 1-2 mm). Current minimallyinvasive techniques increase risk of malposition. The pedicle screw maybe inserted off center, such as, for example, too medial, which mayimpinge on the associated nerve root causing pain. This requires arepositioning of the screw. However, even after repositioning there maybe an effect on the pedicle wall, which can still cause nerve rootirritation. Such procedures are also susceptible to loosening of thescrew.

SUMMARY OF THE INVENTION

Embodiments of the invention are directed to an internal pedicleinsulator implant assemblies and related methods. In this regard, anexemplary embodiment of an internal pedicle insulator implant comprises:a cylindrical wall defining an interior cavity and having a first endand a second end, the cylindrical wall comprising a smooth, non threadedsegment, a rough surface segment, or combinations thereof. In someembodiments, one segment of the wall is of a greater thickness thanother segments of the wall; whereby the pedicle insulator implantshields a pedicle screw that is implanted into the vertebral body andreduces nerve root irritation and diminishes the loosening of thepedicle screw.

Accordingly, it is an objective of this invention to provide an internalpedicle insulator implant assembly for shielding a pedicle screw that isimplanted into the vertebral body for reducing nerve root irritation anddiminishing the loosening of the pedicle screw.

It is also another objective to provide methods for stabilizing asurgical fixture.

Other objectives and advantages of this invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The drawings constitutea part of this specification and include exemplary embodiments of thepresent invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings. The components in the drawings are not necessarily to scale,emphasis instead being placed upon clearly illustrating the principlesof the present invention. Moreover, in the drawings, like referencenumerals designate corresponding parts throughout the several views.

FIG. 1 is a perspective view of a pedicle insulator implant assembly.

FIG. 2A is a top view showing an embodiment of the cylindrical wall.

FIG. 2B is the side view of FIG. 2A.

FIG. 2C is a top view showing another embodiment of the cylindricalwall.

FIG. 2D is the side view of FIG. 2C.

FIG. 2E is a top view showing a further embodiment of the cylindricalwall.

FIG. 2F is the side view of FIG. 2E.

FIG. 2G is a top view showing yet a further embodiment of thecylindrical wall.

FIG. 2H is the side view of FIG. 2G.

FIGS. 3A-3C are segment views showing various embodiments of the roughsegment of the cylindrical wall.

FIG. 4 is a segment view showing the cylindrical wall with alongitudinal slot extending from a first end to a second end, and havingone segment of the cylindrical wall thicker than the other.

FIG. 5 is a segment view showing the cylindrical wall having one segmentof the cylindrical wall smooth and thicker in width as compared to theopposing segment which is rough and th in width. The smooth thickersegment is placed to protect the nerve from the pedicle screw.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the invention,its application or uses. Embodiments of the invention may be practicedwithout the theoretical aspects presented. Moreover, the theoreticalaspects are presented with the understanding that Applicants do not seekto be bound by the theory presented.

It should be understood that numerous specific details, relationships,and methods are set forth to provide a full understanding of theinvention. One having ordinary skill in the relevant art, however, willreadily recognize that the invention can be practiced without one ormore of the specific details or with other methods. The presentinvention is not limited by the illustrated ordering of acts or events,as some acts may occur in different orders and/or concurrently withother acts or events. Furthermore, not all illustrated acts or eventsare required to implement a methodology in accordance with the presentinvention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Definitions

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges, and are also encompassed within the invention, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Furthermore, to the extent that the terms “including”,“includes”, “having”, “has”, “with”, or variants thereof are used ineither the detailed description and/or the claims, such terms areintended to be inclusive in a manner similar to the term “comprising.”

As used herein, the term “segment” is used to denote a geometric sectionof the cylinder. For example, if the height of the cylinder is denotedas h, and the half-axes, equal to the radius in the case of an roundcylinder, are denoted as α and β, the angle between them, denoted as γ,would represent the size of the “segment”. The larger the value of γ,the larger the segment which can encompass the entire height of thecylinder or parts thereof. For example, the segment may taper off suchthat the top end of the cylinder has a thicker wall than the bottom endof the cylinder. Standard mathematical equations can be used tocalculate surface areas, volumes, etc.

As used herein, the term “cylinder” is used to encompass any cylindricalgeometry, e.g. parabolic, elliptic or hyperbolic geometries.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

Pedicle Insulator Implant

Embodiments of the invention are directed to a pedicle insulatorimplant. The implant is designed to protect the nerves and surroundingtissue from injury by pedicle screws or other surgical devices andinstruments. In some embodiments, the implant comprises both a rough andsmooth surface area on opposing segments of the implant. The roughsurface area is desirable in situations to provide further grip of theassembly and prevent rotation during the insertion of, for example, apedicle screw. In other embodiments, the insulator implant comprises asegment of the implant having a thicker wall which is positioned betweenthe pedicle and nerve.

With the advent of pedicle screw technology none of the devices provideprotection when inserted into a patient. There is very limited tolerancebetween neural structures and a pedicle screw since the inferomedialaspect of the pedicle is an area of neural structures and hence a“danger zone.” There is only a 1-3 mm between a nerve root and a pediclescrew. In addition a lateral breach compromises fixation. Due to thevery small margin of error, many pedicle screw implantations result inthe malposition of the screw.

Pedicle screws also become loose over a period of time. This is verycommon in elderly who are osteoporotic (44 million currently at risk inthe U.S.) and also as the aging population is more active resulting in ademand for more extensive procedures. Lateral breaches compromisefixation which creates loosening and pseudarthrosis results whenconstructs loosen over time. Most pedicle screws are left inpermanently, not temporarily as approved by the FDA, which can result inloosening over time. Some of the traditional pedicle screws have rodsresulting in increased number of problems, for example, with longconstructs for degenerative scoliosis or with distraction to correctdeformities. The pedicle insulator embodied herein is designed toovercome these and other problems and disadvantages associated withpedicle screws.

In some embodiments, the implant comprises one or more biocompatible orinert materials. For example, the segment having a greater thickness maycomprise a “softer” smoother material than another segment. In otherembodiments, the implant is uniform in the type of material used.Examples of materials include without limitation: titanium, or anyconventional material used for surgical implants, such as stainlesssteel and its many different alloys, titanium alloys, metallic alloys,polymeric materials, plastics, plastic composites, ceramic and any othermetal or material with the requisite strength and biologically inertproperties. However, it is to be understood, that the various parts ofthe implant may be constructed from various materials. For example, thesegment having a thicker wall may be made from a material that providesthe requisite strength but also flexibility, whereas another segment maybe made from a rigid material. In some embodiments, the insulatorimplant may comprise one or more layers of materials, such as, forexample, plastic, polymers, metals or any other biocompatibleconventional material(s). In other embodiments, the implant may becoated with a biocompatible material, for example, medical gradethermoplastic elastomeric compounds. In other embodiments, the insulatorimplant comprises polyether ether ketone (PEEK) or a composite of PEEK.

FIGS. 1 through 5 which are now referenced, illustrate the presentinvention and the manner in which it is assembled. Like referencenumerals refer to like components in the various figures. FIG. 1 showsone embodiment of an internal pedicle insulator apparatus 10. Theinternal pedicle insulator apparatus 10 comprises an outer insertion rod11, and an internal pedicle insulator implant 12. A fixture sized andshaped can be inserted within the cavity 20 defined by an inwardlyfacing surface of the pedicle insulator implant. In some embodiments,the pedicle insulator is curvilinear having a radius of about 10 degreesto 360 degrees and any degree therebewteen. In other embodiments, thepedicle insulator is curvilinear having a radius of about 120 degrees toabout 180 degrees and any degree therebewteen.

The outer insertion rod 11 has a lower end 13 and an opposing upper end14. An opening 15 is disposed at the lower end 13. An optional handle 16can be disposed toward the upper end 14 of the outer insertion rod 11 tofacilitate use of the internal pedicle insulator apparatus 10. Anopening at the upper end 14 of the outer insertion rod 11 through whichthe pedicle insulator implant 12 can pass can also be included (notshown). It is preferable that the outer insertion rod 11 has asubstantially round cross-section. It should be noted, however, that theouter insertion rod 11 can comprise any suitable cross-section. Theouter insertion rod 11 can comprise titanium, however, it should beunderstood that the outer insertion rod 11 can comprise any suitablematerial.

The outer insertion rod 11 is arranged and configured to receive thepedicle insulator implant 12 through the opening 15 disposed at thelower end 13 of the outer insertion rod 11. The pedicle insulatorimplant 12 is preferably slidably inserted into the outer insertion rod11 such that the upper end 14 of the outer insertion rod 11substantially corresponds to the top end 18 of the pedicle insulatorimplant 12. Similarly, the lower end 13 of the outer insertion rod 11substantially corresponds with the bottom end 19 of the pedicleinsulator implant 12. The pedicle insulator implant 12 is laterallyslidable within the outer insertion rod 11.

In one embodiment, a pedicle insulator implant, implantable in avertebral body of a spine, comprises a cylindrical wall 12 defining aninterior cavity 20 and having a first end 18 and a second end 19. Insome embodiments, the length of the implant is from about 5 mm to about40 mm from the first end 18 to the second end 19. In other embodiments,the insulator implant is about 10 mm to about 20 mm in length from thefirst end 18 to the second end 19.

The cylindrical wall 12 comprises a smooth, non threaded segment 21 anda rough surface segment 22, or, the cylindrical wall is uniformlysmooth. In embodiments, a segment of the cylindrical wall is thicker inwidth than the rest of the cylindrical wall. In some embodiments, thesegment of the cylindrical wall having a smooth surface is of a greaterthickness than the segment having a rough surface. Referring to FIGS.2A-2H, whereby the thickness of the wall comprising the smooth segmentis denoted T_(S) and the thickness of the wall of the rough segment isdenoted T_(R), T_(S) is always greater than T_(R). In some embodiments,the thickness of the wall of a segment of the smooth surface T_(S) isuniform in width, but thicker than the rest of the wall. In otherembodiments, the thickness T_(S) is greatest at the midpoint of thesmooth segment. If this point is denoted T_(S0) the thickness of thewall decreases as the rough segment of the wall is approached. Thesethicknesses are denoted T_(SX) and T_(SY) and define the point whereinthe width of wall is equal to the thickness of the wall having a roughsurface. In this embodiment, T_(S0)>T_(SX) T_(S0)>T_(SY) andT_(SX)=T_(SY)=T_(R). (FIGS. 2A, 2C). In other embodiments, the thicknessof one segment of the cylindrical wall increases gradually in thicknessT_(R) so that the thickness of the wall at either T_(Y) or T_(X) isgreater than the thickness T_(R) (FIG. 2C). In FIG. 2E, the thickness ofthe wall increases gradually from T_(RO) the thickness of origin.

In another embodiment, the cylindrical segment comprises a smooth andnon-threaded surface directed inwardly and outwardly (FIG. 2C). Thethickness of the wall of one segment T_(R) is less than the thickness ofthe wall on the opposing segment T_(S). The thicker segment of the wallis the side of the cylindrical wall which would shield a nerve or othertissue from damage while the thinner segment of the wall allows for thepedicle screw to deform the thinner wall segment as the pedicle screw isdriven into the bone. The sizes of each segment of a wall can vary. Insome embodiments the thicker segment surface area is equal to thethinner segment surface area. In other embodiments, the thicker segmentsurface area is greater than the surface area of the thinner segment. Inother embodiments, the surface area of the thinner segment of the wallis greater than the surface area of the segment with the thicker wall.In other embodiments, the cylindrical wall comprising the smooth, nonthreaded surface comprises at least about 25% of the cylindrical wallsurface area. In another embodiment, the segment of the cylindrical wallcomprising the smooth, non threaded surface comprises at least about 25%of the cylindrical wall surface area.

In other embodiments, the cylindrical wall is non-continuous andcomprises a longitudinal slot 23 extending between the first end 18 andthe second end 19, the longitudinal slot forming opposing sides 24 and25, each opposing side 24, 25 ending facing each other (FIG. 2A).

In another embodiment, the cylindrical wall is non-continuous and theopposing segments 24, 25 of the cylindrical wall overlap each other, theone segment extending into the interior cavity 20 (FIGS. 2G, 2H). In oneembodiment, the smooth segment of the cylindrical wall 21 extends intothe interior cavity. In another embodiment, the rough segment extendsinto the interior cavity. In either case, the extension of eithersegment allows for a greater surface area and to accommodate pediclescrews of any size, width and shape.

In other embodiments, the cylindrical wall is continuous (FIGS. 2C-2F)having a smooth, non-threaded segment of the cylindrical wall which isinwardly and outwardly directed, that is, uniformly smooth. In otherembodiments, the cylindrical wall is continuous (FIGS. 2C-2F) having asmooth, non-threaded segment of the cylindrical wall which is inwardlyand outwardly directed and a rough segment having an inwardly oroutwardly or both inwardly and outwardly directed rough surface. Inother embodiments, the cylindrical wall comprises an outwardly directedsmooth surface and an inwardly directed rough surface.

In embodiments wherein the pedicle insulator comprises a rough surface,the surface of the wall comprises threads (FIG. 38), protrusions, teeth,barbs, fins or combinations thereof (FIGS. 3A, 3C).

In another embodiment, the pedicle insulator implant further comprisesan outer cylindrical wall defining an interior cavity and having a firstend and a second end. In some embodiments, the outer cylindrical wallcomprises an inwardly directed smooth and non threaded surface,dimensioned to allow slidable insertion of the cylindrical wall.

In another embodiment, a pedicle insulator implant, implantable in avertebral body of a spine, comprises a wall 12 defining an interiorcavity 20 and having a first end 18 and a second end 19. In oneembodiment, the wall comprises a smooth and non-threaded inwardly andoutwardly directed surface, or a smooth and non-threaded outwardlysurface and a rough inwardly directed surface, a segment of the wallbeing of a thicker width than other segments of the wall. The wall canbe of various shapes and can be dimensioned and shaped to fit pediclescrews of varying sizes and shapes. In one embodiment, the wall isnon-continuous and comprises a longitudinal slot extending between thefirst end and the second end. In another embodiment, the wall isnon-continuous and a segment of the wall extends within the hollowcenter, the inwardly directed surface of one segment 24 facing theoutwardly directed surface 25 of an opposing segment. In anotherembodiment, the wall is cylindrical and continuous. In otherembodiments, the segment of the wall comprising the thicker widthcomprises at least about 25% of the cylindrical wall surface area.

In another embodiment, an outer wall defining an interior cavity andhaving a first end and a second end. This outer wall comprises aninwardly directed smooth and non threaded surface, dimensioned to allowslidable insertion of the pedicle insulator implant (FIG. 1).

In another embodiment, a pedicle insulator implant assembly implantableinto a vertebral body of a spine comprises: an inner wall 12 defining aninterior cavity 20 having a first end 18 and a second end 19 (FIG. 1).The inner wall comprises a smooth surface segment, a rough surfacesegment or combinations thereof. In addition, the inner wall 12comprises a segment of the inner wall which has a wider or thicker widthas compared to other segments of the inner wall. In some embodiments theassembly comprises an outer wall 11 defining an interior cavity andhaving a first end 18 and a second end 19. The outer wall having aninwardly directed smooth and non threaded surface dimensioned to allowthe inner wall to slidably fit into the outer wall.

In some embodiments, the inner wall 12 comprises: a longitudinal slot 23extending between the first end 18 and the second end 19, anon-continuous wall and a segment of the wall 24, 25 extends within thehollow center 20, a continuous wall or combinations thereof (FIGS. 2A-2Hand 4).

In some embodiments, the pedicle insulator implant 12 is cylindrical,the distal end of the pedicle insulator implant being annularly tapered.

In some embodiments, the assembly further comprises a fixture sized andshaped to be inserted within a cavity defined by the inner wall of thepedicle insulator implant. In some embodiments, the fixture is a pediclescrew.

In another embodiment, a method for stabilizing a surgical fixturecomprises placing an implant at least partially about an intermediatesegment of the fixture, the implant having a longitudinal slot and asegment of the implant having a thicker wall on one segment of theimplant. The distal end of the implant is driven into the tissue inwhich the fixture is inserted such that the thicker and smooth segmentis located between the outer surface of the implant and a nerve ortissue to be protected. If desired, the implant comprises a segment ofwhereby the surface is rough, e.g threaded, barbed etc., to providefurther gripping of the implant to a bone. In some embodiments, thefixture is inserted into the tissue prior to the driving step. Placingof the implant comprises urging the intermediate segment of the fixturethrough the slot such that the fixture, e.g. a pedicle screw, isreceived within the cavity defined by the inner wall of the implant.

The unique features of the implant, e.g. the thicker smooth segment anda thinner segment, reduces a tendency of the fixture to toggle and also,increases pullout strength of the fixture.

The invention has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated that those skilledin the art, upon consegmentration of this disclosure, may makemodifications and improvements within the spirit and scope of theinvention.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

All documents mentioned herein are incorporated herein by reference. Allpublications and patent documents cited in this application areincorporated by reference for all purposes to the same extent as if eachindividual publication or patent document were so individually denoted.By their citation of various references in this document, Applicants donot admit any particular reference is “prior art” to their invention.

What is claimed:
 1. A pedicle insulator implant, implantable in avertebral body of a spine, comprising: a non-continuous cylindrical walldefining an interior cavity and having a first end and a second end; afirst segment of the cylindrical wall comprising a smooth exteriorsurface; and a second segment of the cylindrical wall comprising a roughexterior surface, wherein: i) the first segment of the cylindrical wallis of a greater thickness than the second segment of the cylindricalwall; and ii) the first segment comprises a first material and thesecond segment comprises a second material, whereby the pedicleinsulator implant is configured to shield a fixture, reduce nerve rootirritation, and diminish loosening of the fixture, when the fixture isimplanted into a vertebral body.
 2. The pedicle insulator implant ofclaim 1, wherein the first material and second material arebiocompatible or bioinert materials.
 3. The pedicle insulator implant ofclaim 1, wherein the second material is more ridged than the firstmaterial.
 4. The pedicle insulator implant of claim 1, wherein the roughsurface comprises threads, protrusions, teeth, barbs, fins, orcombinations thereof.
 5. The pedicle insulator implant of claim 4,wherein the rough surface comprises substantially triangular-shapedprotrusions.
 6. The pedicle insulator implant of claim 4, wherein aportion of the second segment of the cylindrical wall overlaps a portionof the first segment of the cylindrical wall, extending into theinterior cavity.
 7. The pedicle insulator implant of claim 6, whereinthe fixture is a pedicle screw.
 8. The pedicle insulator implant ofclaim 7, wherein a distal end of the implant is annularly tapered.